Phthalic anhydrid



C. E. ANDREWS. PHTHALIC ANHYDRID.

APPLICATION FILED OCT. 14, I919.

1,336,182. Patentd Apr- 6,1920.

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HES'EIZER E. ANDREWS, 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO THE SELDEN. GOMEANY, OF PITTSBURGH, PENNSYLVANIA, A GORPQBATIOH OF PENN$YLVANIA.

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Specification of IettersEatent.

Patented Apr. c, 19.20.

Application filed iictober 14,1919. Serial No. 336,560. I

To all whom it may concern:

Be it known that I, Cnnsrnu E. Auonnws, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented cer tain new and useful Improvements in Phthalic Anhydrids, of which the followia V 'b is a specification.

The present invention has for its object a commercial article of manufacture, phthalic anhydrid, w -ich is substantially chemically pure. E 1 thalic anhydrid of this land may be manufactured in accordance with processes hereinafter described. Que such process consists, of forcing a mixture of a temperature of about 350 to 550 (3., (preferably about 150 C.) over or throu h a suitablecatalyst such as molybdenum oxid. There is thereby produced a mixture consisting essentially of phthalic anhydrid and other oxidation products of naphthalene, such as phthalic acid, l-lnapthoquinone, benzoic acid, some water, and some unchanged naphthalene, which mixture may be then led to a condenser and condensed or fractionally condensed, and the resultant products suitably separated. The reaction product may then betreated in an apparatus as hereinafter described.

In t 1e accompanying drawings, the figure is a vertical sectional view through one type of apparatus that may be employed.

In said apparatus the said reaction product as produced by the before mentioned oxidation process is introduced into a closed container 1 by means of a filling funnel 2, or through any other suitable instrumentah ity, and is heated by any suitable means, as for instance, burners'3. A blast of gas suitable for use as a vehicle is passed over the material, preferably being introduced by a centrifugal fan 4 having a discharge nozzle 5 entering one end of the container l. v Baffie plates 6 may be located Within the con-- tamer. The vapor-laden gases are conducted by a conduit 7 into a suitable condenser.

governing the temperatures of the dill'erent compartments, said means being in the form of spray nozzles 12 supplied through branch pipes 13 from a main 14. The residue gas, after passing through the condenser, may be returned through a conduit 15 to the fan l, and provision is made for heating the same, as for example, burners 1-8.

As an example,'phthalic anhydrid, having a melting point or approximately 128 degrees, centigrade,

degrees, centigrade, with which is mixed naphthalene having a melting point of 80 degrees, centigrade, and a. boiling point of. 218 degrees, centigrade, together with other oxidation products or naphthalene, is placed in the container 1, and is subjected to a temperature of between 150 degrees, Centigrade, and 200 degrees, centigrade, the container and the gas being properly heated by the burners 3 and 6 respectively. The gas is one that will beinert at the temperature employed. The vapor laden gas, passing through the conduit 7, is delivered into the condenser, wherein a fractional condensation is efiected, resulting in the crystals constituting the invention, being deposited in the first two or three compartments and on the screens defining the same when said compartments are maintained at a temperature of between about degrees, centigrade, and about 115 degrees, centigrade. Those crystals which are deposited on the screens are dislodged by suitable Weights, as 17, which can be swung against the screens periodically to dislodge the product therefrom.

The phthalic anhydrid produced according to this invention consists of colorless needle-like crystals, is substantially chemically pure, being free from benzoic acid, sulfur, chlorin, mercury, water, and only slight traces of phthalic acid and has a melting point above 130 degrees, centigrade, (corrected).

These characteristics establish this phthalic anhydrid as a new commercial product as shown by its high melting point. As a consequence, many advantages result from its use in the industries. For example, less trouble is experienced in the urification of phenolphthalein made there rom. Certain dyes are obtained in more brilliant shades when this product is used, as for example, various members of the rhodamin group.

and a boiling point 0528i Having thus fully describeu my invention, crystals substantially chemically pure and 10 what I claim as new, and desire to secure by having a melting) point above 130, centi Letters Patent, is grade, (correcte I 1. As an article of manufacture, phthalic In testimony whereof I afiix my signature -5 anhydrid being substantially chemically in the presence of two witnesses.

pure and having a melting point above 130 v CHESTER E. ANDREWS. degrees, centigrade, (corrected). Witnesses:

2. As an article of manufacture, phthalic I G. S. SELDEN anhydrid in the form of colorless needle-like J 0N SELDEN, r. 

